Here is a description of these drugs plus Ativan which is basically the same as xanax:

Ativan (lorazepam)- One book I have says this is "the most potent of the available benzodiazepines".

Tranxene T (clorazepate dipotassium)- "Anxiolytic with actions, uses, & interactions qualitatively similar to those of Ativan but with fewer unwanted side effects, e.g. sedation." This has an onset of 1 hr but a duration of 24 hours, but it looks like it might metabolize to the same metabolite as Valium. Is Tranxene T (immediate release) a strong benzo like Ativan or Klonopin or a weak one like Valium?

Xanax (alprazolam)-
"associated with significantly less drowsiness. Has antidepressant as well as anxiolytic actions".